1. Field of the Invention
The present invention relates to a vehicular lamp and more particularly to a vehicular (tail/brake) lamp that employs light-emitting devices such as light-emitting diodes (LED) as a light source thereof.
2. Prior Art
A vehicular lamp employing a number of LEDs as light sources is popular since it provides a substantial amount of light emission and also provides a luxurious appearance. However, LEDs have a high directivity compared to general bulbs; and thus, so as to emit light from the entire front cover (including the lens) of the lamp, a correspondingly large number of LEDs are required, and this results in a high cost product.
In view of the above, various structures are disclosed in, for instance, Japanese Patent Application Laid-Open (Kokai) Nos. 2002-184212, 2001-283616 and 2002-109907 in order to make lamps appear like a multi-light type lamp (that includes a plurality of LEDs) by dispersing light emitted from the LEDs.
The structures in Japanese Patent Application Laid-Open (Kokai) Nos. 2002-184212 and 2001-283616 employ, as shown in FIGS. 11 and 12, respectively, a construction in which an LED 4 is provided to face forward at a substantially central position of a first reflector 2, and a second reflector 6 is provided to cover the LED 4, so that light emitted from the LED 4 is reflected by the reflectors 6 and 2 and distributed in the forward direction as shown by arrows. Reference numeral 3 denotes lenses that cover the front face of a lamp chamber.
In Japanese Patent Application Laid-Open (Kokai) No. 2002-109907, as shown in FIG. 13, the LED 4 is disposed to face rearward in front of a substantially central portion of the first reflector 2, such that light emitted from the LED 4 is reflected by the reflector 2 and distributed in the forward direction as shown by arrows. Reference numeral 5 denotes a mounting member for mounting the LED 4 to the lens 3. Reference characters f1 and f2 indicate focal points of the reflecting surfaces of the reflectors.
However, in the above-described prior arts, the second reflector 6 and the LED mounting member 5 are provided on the backside of (or behind) the lens 3. Accordingly, a non-translucent portion 3a is required in the lens 3, causing a poor appearance to the lamp when the lamp is not lit.
In addition, to disperse light emitted from the LED having directivity to a plurality of locations, it is necessary that the LED be arranged sufficiently apart from the reflector; and this causes problems that the depth of the lamp tends to be large and also a degree of freedom of design choice is restricted.
There also exists a related art in which a light guiding member provided at an inner side of a lens is made to emit light by an LED, allowing an improved appearance to the lamp when the lamp is not lit and making the lamp thinner. However, this art is designed to emit light from the entire light guiding member having a flat shape (surface emission) and is extremely difficult to make the lamp appear like a multi-light type lamp.
Therefore, the inventors of the present application conceived an idea to let an elliptical surface guide light. More specifically, the inventors assumed that by constructing a light guiding member with an elliptical body and arranging the light-emitting portion of an LED at a first focal point of the elliptical surface of the light guiding member, most of the light emitted from the LED is internally reflected by the elliptical surface and is condensed at a second focal point, thereby emitting light from the second focal point; and, moreover, by way of arranging a plurality of light guiding members each having an elliptical body shape and coupling them in series in such a manner that they share the focal points, light emission is guided up to the focal point of the rearmost light guiding member from the light-emitting portion of the LED, and the light is emitted therefrom. Based on these concepts, a prototype was made, and it was found that such has a great effectiveness of which was confirmed, and the present invention has been created.